The present invention relates to valve assemblies, for example, valve assemblies which are operated to facilitate and/or control fluid flow, and to methods of using same. The present valve assemblies include a valve housing through which fluid, e.g., liquid and/or gas, can pass between an inner or first valve element and an outer or second valve element.
Drain valves, for example, water drain valves and the like, are designed to provide high flow-capacity, leak-proof shutoff and non-freezing operation.
Such valves may utilize a double valve element construction which includes an inner valve and an outer valve that both operate on the same valve stem, for example, permitting the valve chamber, that is, the space between the inner and outer valves, to drain sufficiently before the outer valve is closed.
Because of the advantageous high flow capacity of such valves, the flow rate or velocity of the fluid in the valve chamber is quite high. Also, the fluid, e.g. liquid, being passed through the valve assembly can be, and often is, contaminated with materials, such as solid particles, dirt and the like, which can cause damage to and/or hinder the operation of the valve. It is often not possible or impractical to use mechanical means, such as filters, to ensure that the fluid being passed through the valve is contaminant free.
Because of the double action, single handwheel, single valve stem mechanisms of many of such valves, the valve stem between the inner and outer valve elements includes one or more threaded portions, which facilitate the ability of the single handwheel to open or close each of the inner and outer valve elements, as desired.
Thus, it may be important, even necessary, to have a portion of the valve stem be threaded. Exposing the threaded portion of the valve stem to the fluid (liquid) being passed through the valve can have a number of detrimental consequences.
For example, the threads of the threaded portion of the valve stem can become contaminated, e.g., clogged or blocked, by debris in the fluid being passed through the valve. This can result in the valve not functioning properly or even becoming non-functional. In this event, the valve may have to be taken out of service and cleaned, which can be time and/or labor intensive, and may require shutting down the operation in which the valve is used.
In another circumstance, the threads of the threaded portion of the valve stem are often lubricated, e.g., with grease and the like lubricants, to facilitate the functioning of the threaded portion. With the threaded portion being exposed to a high flow of fluid in the valve, the lubricant may be lost from the threaded portion of the valve stem, which can adversely affect the performance of the valve and result in added cost and/or process downtime. Moreover, the lubricant from the threaded portion may be lost in a product passing through the valve, which may result in unwanted, disadvantageous and costly contamination of the product.
Other disadvantages of having the threaded portion of such a valve stem exposed to large volumes of flowing fluid include, for example, harmful corrosion of the threaded portion; reduced valve life; more frequent and/or more extensive valve service/maintenance and the like.
All of the disadvantages of using a valve with a valve stem having a threaded portion exposed to the fluid being processed through the valve have had to be endured because the functioning of the valve required that such a threaded portion of the valve stem be present.